What Are They?

While
these strange, jelly-like, blobs pose no threat to
lake users, they may cause a fright if you are
unfamiliar with them. Bryozoans
are aquatic animals with a name that literally means “moss animals”.

Bryozoa are colonies of tiny colonial animals called zoids and appear as gelatinous globs up to the size of a
football. Most species are marine animals, however there is one class, Phylactolaemata, that live exclusively in
freshwater. They are often attached to submerged surfaces such as tree branches, roots, rocks, pilings, docks,
etc. Sometimes, a clump that has broken loose can be found free-floating or washed up near the shoreline.

Water Quality Indicator

Bryozoans filter water for their food like sponges and
feed on small micro-organisms such as diatoms and other unicellular algae. Each zoid in the colony has whorls of
delicate feeding tentacles swaying slowly in the water catching food. Some freshwater varieties are thought to be
useful indicators of water quality. It is said that they like water that is eutrophic,
which means very productive lakes with lots of food.

Bryozoa Reproduction

Bryozoans
reproduce by more than one method. When you look at them, there is a large number of tiny black dots visible imbedded
in the jelly. Each of these tiny black dots becomes a statoblast. A statoblast is a cyst, similar to egg or
spore. At the end of summer, as the lake water cools, the bryozoan dies. The jelly dissolves and releases the
statoblasts; when released they look like small, dark brown disks with radiating barbed spikes.

These
statoblasts can remain dormant for some time, withstand drying and freezing, and survive the winter to start new
colonies next year. Reproduction can also occur by budding off new zoids as the colony grows. If a piece of a bryozoan
colony breaks off, the piece can continue to grow and form a new colony.